MR2 Exhaust Upgrade Opinions
From: nmccoy1042@postoffice.worldnet.att.net
Date: Tue, 2 Sep 1997 22:46:42 +0000
Geoff,
I have a document to add to mr2.com if you think it is appropriate.
It is a collection of various opinions on exhaust upgrades from past
mr2-digests. I organized it by model type. Other than removing names and
non-exhaust information, no changes have been made to what was said on the
digest.
Brad McCoy
93t
Mark I Normally Aspirated
putting a 3 inch exhaust on a 4AGE is way too big. Even a 2 1/2 is a bit
large for a normally aspirated 1.6L engine. Your torque band will fall sharply
on the low end with minimal gains at the top end. Just to put things in
perspective, a 3 inch exhaust is already too large on a stock
7MGTE Supra turbo, imagine this on an engine with (nearly) half the
displacement and no forced induction. Just remember that any N/A motor needs
some backpressure for torque.
---
This Sunday I finally got my new Janspeed exhaust for my Mk1. After
installing it (it only took some 30 minutes), I've noticed a couple of
things:
1. The downpipe runs pretty close to the oil pan, and gets hot. While
the original exhaust has a heatshield on it, the Janspeed does not.
The oil does get hotter, and it gets hotter faster as well. I think
I'm going to get some heat insulating material.
2. The mounting bracket for the original exhaust is exactly at the place
the downpipe joins with the system, and the two rub against each
other. It sends vibrations through the car (at least I think it does).
Other than these things, the Janspeed exhaust is brilliant. It
produces a low, impressive tone, with a screaming howl at redline. I
can not recommend this system to people with delicate hearing,
though...:-)
And strangely enough, the car seems to pull stronger at lower revs than
before, even though this system is far more free-flowing than the
original.
MkI normally aspirated cars may benefit by fitting the
exhaust from a 1989 Supercharged car. The lower restritction
should help overall power (according to TRD).
>Ok after some pretty mixed at best reviews of the pacesetter monza
>exhaust system
Unless you plan to retain your iron manifold and your convertor AND like
loud noise, look elsewhere.
Best and cheapest success for me was to make my own.
You'll need help from a muffler guy or someone who can do simple welds.
>I've had my local muffler and brake guy try and sell me a glass pack
>(cherry bomb looking) muffler that was about 8 inches in diameter,and i
>could see my freind at the other end of it. Anyone ever try any thing
>like this if so how did it go. I am mainly concerned with the sound, i
>don't want people to look around and look for a 120cc dirt bike fly by.
Forget it...WAY loud for the street. Glasspacks also get louder as they
break in (or down). The 4AGE has a wicked exhaust note. I did this and a
host of other combos (much to Dave's delight no doubt), all in all, I made 4
exhausts for my MR2 (spending a couple hundred bucks) before I found a
tolerable solution.
>On a Mk1, if I want to lose the small silencer, which for you guys
>State-Side, is a Cat, what diameter pipe should I use to bridge the gap to
>the main end silencer? Or should I stick to the standard diameter already
>being used?
You'd be better off loosing the end silencer. I've replaced that with
a Simonz 'sports'-muffler, and response has improved quite a bit.
I've heard that a Toyota mechanic said something like 'do whatever you
want with the rear muffler, but don't touch the first!'. Don't know if
it's true, though.
>Running a less restricted system like this, where, if anywhere, would I see
>an improvement?
Sound! :-) Really - the sound I'm getting from the exhaust is truly
wonderful, especially driving through tunnels at close-to-redline.
The Janspeed system includes downpipes. Will set you back about 230 pounds
for the complete super sport version (which is alot cheaper than the
standard !!).
You should check out stainless ones. There is one at about 280 pounds
which is only 80 or so more than a Janspeed (mild steel).. and will
obviously last a lot longer. I think it's Magnex that make the
304 stainless by the way....
>What I've wondered about is adapting a superbike muffler to my MKI. They
>flow for far more power than I'm cranking out, and any recent superbike is
>up there with race-built Jaguar sixes for spine tingling musicality. I
>would love to make my toy sound like that! I haven't checked into getting
>one that a shop pulled off a bike when someone decided to go racing, but I
>don't imagine it would be too heinously expensive.
Well...it's do-able, but is LOUD. I made a buncha exhausts this past spring.
I have a nice aluminum canister
Yoshimura muffler. The core is too small for a 1600 cc engine (IMHO). A
generic Supertrapp muffler can be adapted, but is loud also. The sound is
nice, just loud. A typical superbike factory muffler has a very small core
through the muffler and would be pretty restrictive.
Forget these scenarios with a header and street use (WAY, WAY LOUD). A Turbo
muffler and a 180 mandrel bend makes a reasonably quiet muffler (even
without the cat and with a header).
I've found a really knowledgeable and low key shop that does TIG welding
and mandrell bends for exhaust systems. And their prices are very
reasonable too. They'll custom fabricate the necessary pipes and hangers to
put a Borla muffler on my 85 Mk1. If you get a chance, try to see a
cut-away view of the Borla muffler. The exhaust gas indeed goes right
through, with only a 45 degree zigzag in the middle. That's it! All other
mufflers make the gas go through multiple 180 degree bends. And yet the
sound is not any louder. It's definitely way softer than the "performance"
exhaust that I see on the street now with the resonator pipe in the rear.
Coupled to the truly functional (i.e. truly adds performance) TRD exhaust
header, the car should run faster than ever.
I installed the new converter from NAPA (cost $130 retail) & got smog test -
results were great! Just like a new car (car has 140K on it). That'll be an
issue for a lot of you now that the cars are getting older...
There is a lot of talk about mufflers from HKS, TRD, Greddy etc. I purchased
a few years ago a muffler made by Sebring and Austrien company. this is a
really good muffler. The sound on the highway is only slightly louder then
stock, long drives are not a problem. Yet when you lower the window and are
driving around the streat this muffler makes the most awsome sound. The
power increase is not dramatic and I would say equel to the other sport
mufflers. The throughty sound without the resonance and boom though makes
the price, about $350, worth it, and you get two chrome tips on both ends
like the MkII MR2.
has an '86 MR2 and he put a
Sebring Exhaust from Jim Cook Racing on it. The muffler has tips on both
sides like on a Mk2 stock muffler. I'm also considering buying this muffler
since he said he is happy with the sound and power (not too loud, noticeable
increase). He bought the muffler a couple of years ago from Jim Cook. I
called Jim Cook to see if they still had this muffler, and they said that
yes they still do, but that the muffler Ramzi bought was actually for a mk2
MR2, hence the dual tips, and that they also now sell one specifically for
the mk1 ($100 more though!). Anyway, Ramzi mentioned that Jim Cook's old
catalog listed the
muffler he bought, for the Mk1 (not the Mk2) and that the hangers match up
perfectly on his car. He highly doubts as I do that the hangers on the mk1
and mk2 are in exactly the same place making the mk1 and mk2 mufflers
interchangeable. ... Ramzi did
mention that he had to weld the muffler to the cat, since the flange on the
muffler was a little smaller than the one on the mk1 cat. He is supposing
that this is because the muffler was originally designed to be used in
Europe without the cat, not because the muffler is for a mk2.
Regarding the gentleman's question on which exhaust is better for the mk1 NA
MR2, 90% of my sources prefer the HKS. It has been stated to last longer,
perform better overall, look better, and even sound better. I just
purchased a TRD header and when I get some more funds, my choice will
definitely be the HKS exhuast. The Trust has been said to be more free
flowing, but it has been stated here that this is not the best setup for the
4AGE engine for overall power. The HKS is advertised with a 6hp increase
while the Trust is rated for a 10hp increase. But according to Chris Myer
and John Broderick, what is felt and what counts is really Torque. From
what I gather, the HKS offers more Torque increase for a better overall
power increase, something you will feel, and something that will last and
perform. Hope this helps.
I've had several people ask me about the Janspeed exhaust system on my car,
and I thought I'd pass along my thoughts and some info on this system:
Appearence: Killer! looks really sweet with two very large (3.5"?)
resonator tips. If you want to see some good pictures of this system,
check out: http://wwwedu.cs.utwente.nl/~hofste
Power: Very good. I was unfortunate enough to have my pre-Janspeed
exhaust fall off, leaving me running a short straight pipe (downpipe), sans
cats. The power was definately way better without the old exhaust and
converter in place. I was suprised, however, to find that top end power
did *not* seem to decrease with the Janspeed exhaust system in place, and I
swear bottom end torque is actually slightly *better* (?!). I was
impressed.
Quality: Nice. System design and fit are excellent, with a beautiful
2-into-1 downpipe, 1 into 2 Y before the muffler and great welds. This
thing is solid! My only wish is that this thing was made of stainless
steel. I don't remember what alloy is used, but it is covered in a
heat-resistant black paint that needed to be touched up after I put it on
the car.
Instructions: None, at least I didn't get any and didn't need them.
Sound: Good. Quieter than I expected, especially comparing to the full
turbo-back HKS exhaust system on my Starion. At low RPMs, this system
seems quieter than the cheap aftermarket exhaust that was on there, with
less high frequency noise. Noise while cruising on the highway is well
supressed. The tone is very good overall, with a nice sound at high RPMs.
I have not yet heard another high-perf exhaust on an MR2, so I can only
compare to my Starions HKS, which is both louder and more aggresive
sounding.
Other parts needed: I bought two gaskets directly from Toyota to go
between the stock manifold and the new downpipe, and three replacement nuts
for bolting them together.
Challenges/frustrations: The Oxygen sensor- for some reason, my '88 had
the O2 sensor on the downpipe, just back of the oil pan, and the Janspeed
exhaust had no such provision. I started to panic, thinking I would have
to have a fitting welded onto this new baby. I found that the exhaust
manifold had a mount for the O2 sensor as well, so I relocated it there,
but this required splicing the sensors harness to lengthen it. Why the
H*ll did Toyota have two different Oxygen sensor mounting locations?
Price: I paid $557.86 U.S. for the full system (including downpipe and
shipping), and another $14 or so for customs. Expensive, ya- but I would
do it again, for it was the only high-quality performance exhaust I found
that was't just cat-back. If I had gone with a cat back system, I would
have needed a replacement downpipe ($135.02 from Toyota), and another
converter ($$).
Availability: I could not find anybody in the U.S. carrying Janspeed.
Talk to Simon Lee at Janspeed Engineering in Salisbury, England:
44-1722-321833, and if you're calling from the U.S., let him know that.
Shipping is very expensive, and you may ;) find him willing to work with
you. Also available from Demon Tweeks: 44-1978-664466-call both to compare
pricing.
Straight pipe after the cat on a Mk1 = L O U D !!!!!!
I had this setup on my Mk1 after my original Toyota muffler rusted out. I
actually had a glasspack (12" long) muffler and a dual resonator tip to try
and quiet (yeah, right) the beastly noise. The muffler shop used the elbow
portion of the old muffler, added a straight piece of pipe, the glasspack,
another elbow and the tip out the stock location, using the stock hanger
mounts from the old muffler.
This setup is loud and the sound grows exponentially as speed increases. At
80 mph on the highway, it felt like 10,000 chainsaws were chasing me! Sure,
it seemed to give more power overall, but I never dynoed it, so I can't
really be sure.
This *may* be okay for autox, but on the street, it's just too loud. After my
dad bought me a stock muffler (he didn't like waking up in the middle of the
night when I pulled into the driveway) it sounded like the engine wasn't
running at all. Now, with my HKS setup, the tone is nice, but not nearly as
loud as with the straight pipe.
Long post? Perhaps. But people wrote me telling me not to go with the
straight pipe when I did it 3 years ago and I didn't listen. I wish I had. I
think I'm partially deaf now from the month or two that I drove around with
ghastly exhaust noise. Or maybe it was all the rock concerts...
>I own a MK I 87 NA. I purchased the Monza free flow muffler from JC
>Whitney. Although it is a bit noisy inside the car, the increase in
>performance was very significant. It also looks good and sounds good. The
>price was about the same as the stock Toyota muffler.
I also have the Monza exhaust system on mine. It is a nice-looking,
quad-outlet unit, but I do have doubts about its longevity. Again, I bought
it because it was only US$108 shipped, but I'm not sure how well it flows.
Also, it turns the car into a booming resonator at 3200-3800rpm. Yes, I
know I shouldn't be down that low, but on the highways here in the US,
maintaining the 76mph it takes to get above this zone can play havoc on
your license. On the good side, it sounds great above 4300rpm. I also
had to do some minor revisions to get mine to fit properly, but some of that
may stem from mating it with the TRD header. I noticed slight gains with
mine, but as I mentioned it was paired with the TRD header and K&N air
filter.
I put the same Monza on my '85 MR2 and removed it within 6 weeks.
Gripes:
1. Loud, and not in a nice way. terrible resonance problem at about 3K rpm.
2. Ugly as sin (personal opinion here).
3. No performance gain whatsoever (actually some loss at below 3-4K, no gain
above).
4. Stinks, literally.
5. Did I mention it was loud?
Cons:
1. Relatively cheap.
2. Returnable to JC Whitney for full refund.
Now, let me say this. I owned an '84 RX-7 and had Monza on it. It was VERY
nice, low rumbling sound, fit perfectly. The only problem, it stunk for the
first 2 weeks until the paint (mostly yellow inside the tips) burned off.
And the chrome got pitted almost immediately.
Now, either Pacesetter has gone down hill since '90 or the muffler thay use for
MR2 is not designed for the car. The latter is probably the case, they just
copied ANSA. It does not fit, requiring some cutting (unexcusable for the
company like Pacesetter).
All in all, the experience I've had with this one was very poor. I talked to
Pacesetter. They were very nice and polite. They said, essentially, "Return it
if you don't like it". Which is what I did. Then I had a regular Toyota muffler
installed for $135 (a blesphemy, I know). It, however, gives me a lifetime
warranty, which is saying something in Rochester, NY.
BTW, be very careful. You will probably soon hear what sounds like valve
tapping. What it actually is, is a leak in the o-rings in the exhaust between
the flexer pipe and the muffler. The upside that you will actually not hear it
with Monza :-)
I had the stock exhaust manifold with cat and HKS exhaust, and it seemed to
give good power throughout the power band and decent torque. I replaced the
manifold with the TRD header and removed the cat (thanks RBC), and now the
seat-o-the pants meter says the torque has moved to higher revs. Not really
a surprise, but I definitely notice a difference. Is there more? Not
sure... but I felt like there was more in the higher revs at the track... but
if I was in too high a gear coming out of a corner... forget it.
The really good thing that happened was the change in exhaust note. I found
that with the cat and stock exhaust manifold the HKS was too quiet. Now,
with header and no cat the car sounds SWEET! No, it's not obnoxiously loud,
and it's quite pleasant in the car at all revs. You just hear a little of it
at cruising speed and it doesn't have any of that mind blowing bass resonance
that you can get in MK1s. I asked yesterday how it sounded when I
autocrossed and they said "Great! Makes you say 'Hmm.. what's that?'" and
take a look. :-)
Mark I SuperCharged
'88 Mk 1 sc. I have the same model and installed the HKS system a
year ago. Before that I experimented with two cheaper alternatives: a
straight-thru glass pack muffler and a JCWhitney "turbo" muffler. Both of
these were loud as hell! The pleasure derived as a touring car was ruined.
The HKS system is slightly louder than stock, particularly at lower
frequencies, but not annoyingly so. Subjectively, it provides a boost in
power in the mid-range and top end. Instalation was easy sice the part is
well made. It is heavy since its design incorporates a large tube inside a
larger insulated drum. I think it shows that HKS spent some time
researching gas flow and tuning resonant frequencies. Price was $4oo US,
steep but it will never need to be replaced.
...my 88 SC last year in about an hour. I don't believe there are any concrete
miles of timeframe to change. My dealer thought about 60k. I also have the
HKS exhaust. This is supposed to give about 8-10 more horses. It is quite
loud. I don't think any of the others would really give much more horse. And
as far as noticing in acceleration, 8-10 horse is really not going to be
noticeable. I paid about 300$.
Mark II Normally Aspirated
BTW, on my 91MR2 I use a REMUS exhaust. (REMUS is an Austrian factory for
sports exhaust systems founded by some former Sebring-workers) When I bought
it in 93 it cost about ATS 6000 - I think the Sebring would cost about the same.
I REALLY love the sound and with the 135x75 mm oval tips it looks quite nice.
On the MKII N/A, have a high performance muffler custom installed unless you
really really want the dual exhaust look.
Without the turbo in the exhaust, the NA is rather loud with a straight pipe...
Anyway, I'm running a Borla muffler with its trademark zig zag bend inside
the muffler, rather than the customary 180 degree turns found in most other
mufflers, including your typical $500 HKS unit, and it does improve
midrange and top end performance noticeably. Not just on timed runs, but a
right out of the shop seat-of-the-pants type of improvement.
I told some people that I would write a post on my outcome on an exhaust for
my 93 N/A.
Well to start out their was no way I was going to spend 500-600 dollars on
an exhaust from HKS or GREDDY. So I talked to some people on a different
way to go. Someone suggested that I get a flowmaster for a Z-28 (they are
supposedly similar) . Well I ended up getting a ULTRAFLO. It has a
single 2.0" inlet and a single 2.0" outlet. It's chrome looks ok, the
sound ... well i guess it sounds a little better than the stock one. A
little deeper sound with a little more rumble (if you will) . As far as the
performance, it seems to be about the same. I talked to the guys at TOY
SPORT and they said that I would not feel much performance change with just
changing the muffler and they were right not that I doughted them.
Mark II Turbo
> If a car needs back-pressure, how do you know just how much back-pressure?
> What damage can actually be caused by running a car with not enough
> back-pressure?
I'm not an expert so don't bet your car on this but;
My understanding of the backpressure issue is that it has two
effects. It reduces the amount of fuel-air mixture that escapes
during the intake/exhaust valve overlap and, provides some degree of
inertial supercharging which increases the pressure of the fuel-air
mixture in the cylinder (these aren't really independent effects).
Imagine the motion the air entering the engine experiences through the
exhaust and intake cylinder cycles.
This is most significant for low end performance. Under high engine
loads or positive boost pressures, the restriction producing the back
pressure can limit the flow rate of your exhaust and reduce the amount
of power you can produce. This is why race cars often use through pipes,
and why performance exhausts for turbo charged cars tend to trade low
end power for improved top end performance.
I can't see any damage lack of back pressure could cause, unless you
get so much fuel escaping unburned from the engine that it overheats
the catalytic converter.
Turbos will always respond better when backpressure after the
turbocharger is minimized. This means the largest, free-flowing
exhaust that your ears can live with. Turbo response is also
optimized when the energy of the exhaust gases is high-a
well-maintained ignition system that thoroughly ignites the
air/fuel mixture will make sure boost response is at its optimum.
Manifold boost pressure is determined by the wastegate setting, not
the turbocharger(unless the turbo is undersized.) Air flow to and
from the motor are key topics related to turbocharging a vehicle.
Easier to get more air in and out, better horsepower availability.
I agree, with one caveat: You want to break up the flow from an
axial swirl to turbulent flow as quickly as possible once the exhaust gases
leave the turbine housing. This effectively shortens the exhaust-system
length and resistance to gas flow. The easiest way to do this is with a
_large_ exhaust pipe attatched to the turbine housing and a gradual
reduction in pipe diameter 18-24" downstream. The gases exiting the turbine
section hit a large impedence mismatch and begin a tumbling, turbulent trip
rather than the "smooth", spiraling segue to the outside world
(alliteration intentional :-) ).
At 18-24" downstream, turbulent flow has been safely established.
The pipe diameter can be reduced to whatever diameter would have been used
originally (i.e. 2.5", 3", etc.) and a muffler can be fitted if desired.
The gases will have lost enough energy (heat) at that point that a smooth
reduction down to 2.5 or 3" will not cause exessive backpressure. The
gradual reduction also gives an additional muffling effect.
How do I establish turbulent flow and retain the stock exhaust cats
and downpipes? Use a screwdriver and hammer to knock out all the
catalyst/substrate in the primary cat. converter. The rapid expasion in
size helps to breakup axial flow while appearing stock on the outside. It
doesn't extend 18", but it helps nonetheless. It also reduces backpressure
a bit ;-). FWIW, I also gored out the secondary converter.
Now if I could find a "banjo fitting" rather than the restrictive
elbow that is placed between the turbine housing and the primary cat I
would really be able to flow some exhaust.
Boost creep is a result of inadaquate wastegate capacity, usually brought
on by big reductions in exhaust backpressure.
The solution is to remove the turbo (which doesn't look like an easy
task on a MR2), and do some porting to the internal wastegate.
Specifically, the wastegate opening needs to be enlarged. You do have to be
careful not to enlarge it so much that the wastegate flapper cannot seal
the opening, or boost response will be extremely poor. The other
solution is to increase exhaust backpressure, but since minimizing
backpressure is desirable on a turbocharged car, increasing wastegate
capacity is the better solution.
For relatively reliable boost modifications, I've talked to several
people who modify MR2's who say first lower exhaust restriction and
intake restriction. This means buy an aftermarket exhaust, or put in a
straight pipe. If the exhaust back pressure is too great
when you are really spinning that turbo, it can damage the turbo
bearings or cause cracks in the exhaust housing.
...a straight pipe is the way to go with the '91Turbo
MR2 - your bottom end will suffer, but the faster the exhaust can escape,
the faster the turbo can spool up...
Am currently running a 304 stainless straight pipe just developed by John
Broderick of Mr.2 Performance Products. My car - '93 Turbo - was used as the
template and prototype for this "catback" exhaust. It bolts on to the stock
flange following the stock subcat. The straight pipe consists of a new flange
welded to a 2 1/2" stainless 90 degree mandrel bend. The new flange is
machined to match the stock flange so that stock "o" ring gasket provides a
complete seal. Stock flange bolts are retained. The mandrel bend is swedged
out to 3" dia and a section of 3" straight stainless is welded to the swedged
2 1/2" bend. The 3" is cut at an angle to match the lower valance angle at the
exit tip. The last 7" of the tip is polished and extends beyond the valance
about the same as a stock tip. Two stainless mounting brackets are welded to
the top of the 3" section which align w/ the l.h. stock rubber isolating mount
so the mount duplicates stock. A new, shorter mounting bolt is provided along
w/ nut and washers since the stock bolt is too long and stock nut is welded to
the stock muffler mount. Welds are clean and neat, finished w/ a power wire
brush. Need I say that the fit on my car is perfect?
A black powder coated filler plate is part of the package which fills in the
r.h. stock exhaust tip opening of the lower body panel valance. The filler is
held in place by 3 s.s. screws, screwed into the valance. The overall *look*
is not exactly stock but does not look like an add-on since the r.h. opening
is filled to match the valance. In discussing the system w/ John, I initially
lobbied for a dual pipe setup to match the stock *look*. However, John has run
a number of flow bench tests that indicate that the single pipe exhibits
better flow characteristics than a dual system. The end result is a very good
looking single tip system.
As to performance, there is a slight bottom end turbo lag
but the spool-up is *so* quick I haven't found it to be a problem. The top end
is significantly improved - very much like being kicked when the turbo
provides boost. Coming out of a curve apex is like being catapulted out.
Response is almost instantaneous as long as engine revs are kept up.
As to sound, this is a bit hard to describe. The exhaust produces a very low
pitched, even "burble" at idle - at higher revs the sound changes to an even,
low growl - at full throttle, a low howl. Sounds a lot like a well-tuned
radial aircraft engine to me. When the throttle is backed off, the sound
changes to an even low pitched, heavy purr w/ no "pops", "bloops" or other
sounds often associated w/ straight pipes. The noise level is subjectively
about a 1/3 above the HKS turbo system, certainly a workable level for me.
For those of you interested in a high quality stainless system, contact John
directly at mr2@earthnet.net or 1-800-4MR-2003 for details and pricing. I
understand that the system will be available either with polished tip or brush
finish tip depending upon your preference.
As for spooling, gut out your cats and run a straight-pipe (or
high-performance exhaust) and you will be flabbergasted at how quickly your
CT-26 spools. The little AeroDynes may come online faster, but not by much
and once the CT-26 is spooling, it doesn't have to stop at 12-16psi!
~ 3" exhaust and 2.5" downpipe. You can get a 3" press bent pipe
made for pretty much any car for around US$200. I had mine made
up locally in Canada for C$300 and it has lasted through road racing,
drag racing, street use and auto-x with no ill effects. Make sure
the shop you take it to does ovalized type bending rather than crush
bending. The ovalization just makes the pipe fat at the bends rather
than actually indents into the pipe. Mandrel is nice, but shouldn't
make a huge difference when you're running 3" pipes.
~ 2.5" downpipes can be made rather easily. I gained about
5-10hp from that mod alone.
~ Cat cons suck on our cars, they are very restrictive, mostly because
of the piping used in the cat. The ends are neck down to a very small
size. If you want to remain emmisions legal, you might consider
a high flow cat or check the ends and get larger flanges to accomodate
more flow.
~ For mufflers, the most efficient and reasonably priced are the Ultraflow
units from Dynomax. I belive RS Akimoto uses the Ultraflow 3" on its
applications. I personally use a 2.75" Super Turbo because it's a
little quieter and allows me to hear my turbo induction and CBV noise
better.
I've never had good luck with straght pipes, but I did see one MR-2
owner come to an auto-x out here with a straight pipe from his first
cat back which sounded rather nice! Any good exhaust shop can make
you a nice set of 3" pipes or a single one will likely work better and
be easier to setup.
I dropped my muffler and installed a straight pipe after the 2nd cat.
Spool up is noticeably quicker and the sound level is a little louder than
stock.
I returned the first HKS exhaust from my '91 MKII a little over a year
after I installed it due to rust. I purchased the unit through St. Andre's in
California. St. Andre's sent me a new one (newer design too) no questions asked.
The newere one rusted after a couple years also. I currently run a 2 1/2"
aluminized straight pipe with the cats in place.
In the last Sport Compact Car magazine there is an excellent article
on exhaust systems and their specific effects on N/A and Turbo cars.
The bottom line is get your exhaust as free flowing and non-restrictive
as possible, and that the "myth" of "Turbos need some back pressure" is
just that a myth.
After considering a number of choices for a high flow exhaust for my '91 MR2 Tu
rbo including HKS (heard too many bad things about it), Greedy (only the muffle
r not the pipe is stainless steel), custom system incorporating a high flow muf
fler such as Edelbrock, Dynomax, etc. (single tip), Mr2 PP stright pipe stainle
ss (maybe a little loud, loss of low end) I've purchased and installed a system
from Genie. It is an all stainless steel system including muffler and 2 1/2 i
nch mandrel bent tubing. It is dual tip (the supplied stainless tips are not w
elded but attached with allen screws and they are the best quality tips I have
seen). It has a lifetime warranty, bolts directly on the last cat and best of
all I was able to get it for $545 including shipping. The quality looks to be
excellent (as good as stock). The only draw back is the weight. I have not pu
t it on the scale but is probably about the same weight give or take a few pou
nds as stock.All in all,I thought it was the best compromise between looks, pe
rformance, and price. The only trouble
I had was the first unit that they shipped was packaged poorly and the tips an
d piping was a bit scratched up. I called them and they sent a new unit out th
at day (it arrived in 3 business days, UPS picked up the old one).
It had the HKS exhaust on it. The mechanic said that the quality was poor and
he had just finished a weld repair on it. The tips look really nice, but I
don't think you can beat the stock stainless unit for quality. The HKS
and Trust exhausts also sound stock. My personal recommendation for MKII
Turbos: go with a straight pipe or stick with the stock unit.
Can speak from experience on this issue. Bought the HKS unit for my '93T on
7-31-95 and installed it 2 wks. later - so it is 9 mo. old now. Recently removed
it (there is story and alternative here, ask John Broderick for details)
and...THE DAMN THING IS COVERED W/ RUST AT ALL WELDS AND RUST
IS SHOWING UP IN
SPOTS ON THE CAN SURFACES!!! Even the "stainless" tips are rusted where the
baffles are tack welded.
Am very displeased. Having heard that HKS was somewhat prone to rust, I put 3
light coats of high temp paint on the entire unit prior to installation -
excepting the "stainless" tips of course. I didn't know rust would be this bad
and the paint should have made the situation better.
Add the above to the fact that none of the HKS mounting hardware fit and
*displeased* becomes an understatement. Considering the cost - $581 US including
frt. & tax - the HKS is, IMHO, a rip. It is, however, much freer flowing than
the stock unit due to inner configuration and larger pipe diameter. Also,
produces much better sound than stock, but...compared the HKS to the stock unit
which was on the car for abt 2 years - no rust at all. I think that says it all
concerning quality of materials and fabrication. (For those interested, note
that HKS weighs in at 36# while the stock unit weighs 31#.)
When I was looking for an exhaust, I took a look at HKS, Trust, etc. Both AEM
and RPS were recommending a Walker DynoMax UltraFlo 3" exhaust which is 18"
long, stainless, and fairly light. The muffler is less than $100, two pieces
of mandrel bent stainless tubing (2.5" U and 3" L) were $100, and installation
(heli-arc welding of tubing and muffler using stainless rod) was another $100
for a grand total of $300.
It has been on for more than a year and there is no rust except for the steel
brackets holding it on which is to be expected. The welding is superb.
I have an HKS exhaust for the second generation MR2. Good for Solo II racing.
While recently starting up my car, while it's on
blocks, I noticed that there seems to be a little leak just behind the
exhaust tip. Last summer one of my HKS exhaust tips fell off so both tips
have been replaced. The garage that put the tips on appeared to have done a
thorough job welding all around the tips. But what I know notice is that at
the weld where the tip joins the pipe, little exhaust fumes come out from I
guess a tiny leak. Also there is water dripping from just below the spot.
I run Greddy exhaust on my 2 turbos, and have been happy with them, the tune is
good,
and air flow is great. Only problem I have noticed is a little rust forming on
the connection of pipe and stainless tips.
Regarding the question about a straight pipe exhaust on a MR2T without the
catalytic converters, Blitz makes a system which replaces the cats with a
large diameter exhaust system and free flowing muffler. This system is
ultra-expensive (about $1K for aluminized steel, much more for stainless).
I use a straight pipe after the cats (cost me $60) and it works and sounds
great. The turbo and the cats muffle the sound just enough so that it
sounds like a NA car with a performance muffler. The pipe is not
mandrel-bent, but I don't think it makes much difference. No one in my area
has a mandrel bending machine. I could get a race car fabrication shop to
weld up some mandrel bent sections, but it's probably not worth it.
Someone on this list once said that the engine works best with a little
backpressure after the turbo. He said that no-cats-and-a-muffler or
cats-and-no-muffler both performed about the same and were both better than
no-cats-and-no-muffler.
Essentially, a catback exhaust is a straight pipe (no muffler) that is
installed after the last catalytic converter in the exhaust system. In the
case of the MkII turbo, installation of the straight pipe occurs right after
the factory sub-cat. Mr.2's exhaust consists of a 2 1/2" dia. mandrel bend
swedged out to 3" dia. which then exits in a short section of 3" pipe.
The HKS Turbo Exhaust is essentially 2 relatively open mufflers connected by a
short section of 2" dia. pipe. The HKS system, by virtue of the 2" connector,
provides some backpressure to improve low rpm turbo response. The 2 exiting
HKS tips measure approx. 2 1/2" dia.
As to h.p. increase, HKS claims 11 h.p. using their exhaust alone. My
experience was that the HKS by itself provided very little improvement, but
when coupled w/ a free-flowing intake system, such as the K&N FIPK (which I
used), there was a substantial improvement. Boost levels went from 7.5 psi to
10 psi and chassis dyno tests on my car showed 19 h.p. increase at the wheels.
I also added a 2.2 psi restrictor to the wastegate control tube which
provided another 15 h.p. gain at the wheels, for a total of 34 h.p. increase
as a result of all modifications. A rough translation to engine dyno figures
would be around 52 h.p. gain over published stock figures.
I have not run dyno tests using Mr.2's exhaust, but can say that it
significantly increases top-end performance. There is minimal turbo lag at low
rpm w/ it that is not apparent w/ the HKS system, but the top end is not there
w/ the HKS either. I simply keep engine rpms up and avoid the low rpm lag. The
result is like being catapulted out of a turn apex - full boost is almost
instantly there at WOT. Whether the engine is making more h.p. as a result of
the freer flow obtained from the Mr.2 exhaust, I cannot say w/ absolute
authority (I assume that it is), but certainly what h.p. the engine does make
is made much more quickly. The end result is an increased performance level
over the HKS.
- the HKS system is very heavy - 36# (as compared to the stock system at 30#)
while the Mr.2 exhaust weighs just under 5#. In a light car like the MR2, this
~31# weight savings is significant.
- -the HKS system is not fully stainless (only the tips and exit pipes are) and
is very prone to rust. Mine began rusting badly at all welds, including
stainless welds, 9 months after installation in an area of the US that does
not use salt in winter. Add salt and it would have been completely rusted out
by now. Mr.2's exhaust piping is 304 stainless in entirety and should last the
life of the car unless you bend it.
- - the HKS system cost $580 US while Mr.2's cost is around $270 US (you should
check this w/ Mr.2 - I don't remember exactly). The HKS took about 1 hr to
install once I had purchased a stock gasket from the local Toyota dealer - the
HKS gasket would not fit the stock flange and the HKS flange would not mate w/
the stock flange. Mr.2's exhaust bolted on in 15 mins and came w/ a stock
gasket. Flanges and hanger fit perfectly.
_ the HKS system is fairly quite, producing a lot of subsonics, particularly
at idle. Mr.2's exhaust is also fairly quite at idle w/ a nice, even "burble"
but does not produce subsonics. There the similarity ends, Mr. 2's exhaust has
a deep, rich, throaty tone that is missing in the HKS at operating revs.
Subjectively, the Mr.2 exhaust noise level is about a third or maybe slightly
more above the HKS overall.
I've kept quiet about some vendors products and pricing, but $270. for a
flipping straight pipe???? Stainless or not, 'dats a lot of money
considering OE is almost the same.
Any good muffler shop SHOULD be able to fabricate one of these, in their
garage for less than $100. All it is, is two pieces of pipe, with simple
bends, one flange, two chrome ends and three simple welds. Total material
cost for a shop could not be more than $25.
Well, around here, mandrel bent 304 or 321 is about $50 per shape in 2.5/3",
and depending on how much welding you have to do, labor could easily hit
$100. You can get a straight pipe for $50, but it isn't going to be high
quality stainless, you won't get heli-arced welds, and it won't be nice and
shiny without the addition of some chrome tips that will rust on the inside
and at the welds. Of course, for $270, you could also get a custom built
stainless exhaust using one of the many tubular mufflers available from Borla,
Dynomax, etc, but it wouldn't necessarily be very pretty. Considering there's
probably at least $150 to $175 of materials and labor on the straight pipe,
$270 seems pretty good compared to HKS, Trust.
Mandrel bent stainless? I investigated a turbo-back exhaust system, and the
shop wanted $200 for stainless parts, and $60/hour labor.
I for one would like to know just where this "good muffler" shop is. When I
initially began to search for a replacement exhaust for my '93T, the best
price I could get for a double exit pipe in seamless 304 stainless/mandrel
bends was $1200 US for a one-time fabrication. I graciously declined at the
time, but the more I checked into things, I came to the conclusion that the
figure was not that far out of line for what I wanted. 304 stainless is
expensive, difficult to weld and bend correctly. Most "good" muffler shops
just looked at me as if I were looney tunes. As it turns out, a single pipe
flows better than a double anyway, so it would have been likely that the $1200
would not have produced the results I was looking for in any event.
On prices, have any of you checked Borla prices lately? A 3"d.x7"l. stainless
intercooled tip alone is ~$70 US retail. The best I could do was ~$55 US. In
addition, that tip is not that well made. I got one - sent it back. The welds
are ragged and covered in slag. Further, portions of it are nothing more than
a press fit that may or may not hold up to the rigors of the MR2 under full
power. Pardon me, but $25 in materials *just don't cut it*. A single 2 1/2"
d. seamless 304 stainless mandrel 1/4 bend is ~$35 US - wholesale, ~$48 US
retail. I've checked. Note that these last are NOT Borla prices.
Then there's the question of fabrication...Is the flange machined to match the
factory? Will it properly mate w/ the remaining cat flange? What gasket is
used? Will it leak? What about these 3 simple welds? Are they TIG welds or
just hacked together w/ an arc welder? Are they neat,clean? Have the welds
been power wire brushed and checked for integrity? Is the tip polished or just
raw stainless? Did you forget about the hanger bracket? Is that stainless?
Then what about mounting hardware...is that all stainless as well? Next, what
do you do w/ the gaping hole on the r.h. side of the valance? Do you provide a
false tip? And just how is that securely mounted? What does that false tip
cost? Or do you provide a filler plate for the opening? Is it painted (subject
to rust) or powder-coated? Is stainless mounting hardware provided for the
filler plate?
None of the above even considers the prospect of going into production w/ the
requisite fabrication of appropriate jigs and templates to do that. It also
doesn't consider the R&D time spent by the developer. Remember, time and tools
are money which have to be paid for somehow - otherwise the developer goes out
of business.
The long and short of all this is that $270 US just *ain't* all that much to
pay for a well thought-out, complete piece of hardware that will last the life
of your car, whether it be a "flipping staight pipe" or not.
I was out Friday getting a straight pipe put on my 93T. I agree that
$270 for a brushed tip straight pipe was a tad expensive, not to mention
the $305 for the polished tip. So I went to the Alamo Autosports in the
Dallas area and they built me the same thing with a 4" resonator tip for
$170. I still think that's a little expensive but the tip alone was
$90! I had 2 stock exhaust so they used the piping off one of my stock
exhausts to get the bends and flange. It looks really nice and it comes
out of the drivers side. I agree on the performance
differences over the HKS system. I had the HKS on my 91T. The HKS
system is no louder than stock. The straight pipe gives more
performance for the money. I went down to the Texas Motorplex Friday
night and ran a best time of 14.557 @ 96.12 MPH. It was very hot and
humid that night and everyone there was running about 3-4 tenths slower
than normal.
you can hammer the cats out with a chisel and use the same exhaust
pipes. the converter is this ceramic material that turns to dust when you
hammer on it or drill it. just scrape out the cats and put the pipes back
on. or you can have custom ones made, although this may be expensive. the
cats really improve the turbo, but destroy any low-end performance. they
restrict the flow much more than the muffler does, so as a result the turbo
will spool slower, but hit much harder. my 93T has no cats or muffler.
its is loud as hell (read: LOUD AS HELL) and when the turbo is spooled the
car is very fast. but it makes driving much harder because you have to use
three foot braking to keep the turbo up, or suffer lag out of corners.
after trying the cat removal route, i would recommend against it
unless you have a heavily modified MR2. the cats provide critical back
pressure, so unless your engine has a higher compression ratio or 500HP,
you will easily get spanked by a car with less horsepower but better low
end response. removing one might be a nice compromise, tho.
I eliminated my secondary cat by simply replacing the whole exhaust
system with one that Trust has for off-road use. It connects onto the
primary cat and is in 3 pieces unlike the stock system which is in two
pieces. I bought it from Toyomoto in Miami, FL. The only problem I have
with it is its not stainless steel. I compared it to the standard Trust
muffler and I like it better.
If you want to remove the pipe that has the secondary cat installed on it
your either going to have to hollow it out or remove the pipe completely.
Removing the pipe completely requires a lift. Not an easy task since
removing any emission systems is against the law!
Perhaps a better way to achieve what you are after - improved performance -
will be to leave the subcat in place and install a catback exhaust or straight
pipe. You will see a *significant* improvement over your current setup.
Without a freeflowing exhaust, you are not realizing the full potential of the
AirInx filter. I have K&N FIPK on my car and have run stock muffler, HKS Turbo
exhaust and straight pipe w/ the K&N. Of these, the straight pipe provides the
best performance. Leaving the subcat in place reduces the noise level of the
pipe and gives additional backpressure, reducing turbo lag associated w/ a
very open exhaust. There is, however, a noticeable lag in turbo spool-up w/
the straight pipe even w/ the subcat in place. But, if you keep the revs up to
around 3k or so, you don't really feel it. Boost is produced very quickly w/
the straight pipe so what you *do* feel is a decided kick, very much like
hitting an afterburner, when the turbo comes up. By comparison to the stock
muffler, its like being hit w/ a hammer. Going back to the stock muffler from
the staight pipe, as I recently had to do, is like dragging a huge boulder
behind the car...absolutely no fun!
Concerning the GReddy muffler, consider that the GReddy has been reported to
be worse abt rusting out than the HKS. From experience, I can assure you that
the HKS is VERY prone to rust. Mine began serious surface rusting after 4 mo.
on the car and the accursed thing cost $580! (A long story,the short of which
is that HKS would not replace the exhaust but finally agreed to give me an
extended warranty.) If I had it to do all over again, I would not have spent
the money on the HKS. Instead, I would have bought John Broderick's stainless
straight pipe kit to begin w/ - a superior piece of work, beautifully executed
w/ polished tip. IMO, a bargain at around $300. Kit includes stainless pipe,
stainless mounting hardware, stock ceramic flange gasket, powder-coated filler
plate for the r.h. valence opening.
I just removed the straight pipe exhaust from my '94T and put the stock
muffler back on, and I swear that the car pulls harder now. It's not just
low end power, either. It seems stronger all the way from idle to redline.
I also swapped cars with another MR2T driver at an autocross test day once
and we both felt that my stock-muffled car pulled stronger than his
straight-piped car. However, this could be due to other differences such as
manufacturing tolerances or the fact that his car is older.
All the fast autocrossers use the straight pipe, swearing that it allows the
turbo to spool up quicker and gives better performance...
I have not done any "real" tests, but I noticed that mine starts to spool up
at around 2200 with a straight pipe while it spooled at around 3000 with the
stock muffler. Just your standard 2.75" pipe w/ 1 mandrel bend, $70 at Midas.
Running the stock muffler will give you more low end torque, but you're not
supposed to be on that end of the power curve when your autoxing, at least
not if you want to be on par with Bob, Stacy or Kevin!
I run a straight pipe in place of the stock muffler on my 91 Turbo primarily
for the weight savings. The catalytic converters are still in place. When I
first tried the straight pipe I did several acceleration runs with the
muffler, then several with the straight pipe, then several more with the
muffler and finally more with the straight pipe. These runs were done on
exactly the same stretch of roadway, same day with atmosperic conditions
stable. I drove in second gear holding engine speed at a constant 2500 rpm
until I reached a road sign that I used as a landmark. I then floored the
accelerator and measured the time required for the car to accelerate to the
rev limiter. I don't have my data here in front of me but I clearly
remember that the difference was in the hundreths of a second with the
*muffler* being the slightly quicker setup. Since I was timing with a
handheld stopwatch I don't think the hundreths of a second difference is very
significant.
Toyota did a very good job with the stock muffler. It sounds good, is
durable and performs very well. It is a little heavy but that is likely the
compromise required to achieve the three benefits listed above.
My straight pipe is on the car because it weighs about 28 lbs. less than the
stock muffler and I do like the more aggressive sound.
I believe there is an explanation as to why a straight pipe appeared to offer
no performance improvement. Bear in mind that I'm no turbo expert so those
of you that are more knowledgeable on this topic please correct me on any
errors I make.
Exhaust back pressure with a good muffler vs. a staright pipe probably varies
by an extremely small amount when compared to the pressure drop across the
turbo impeller when producing usable boost. At the same time it is widely
accepted that some back pressure in the exhaust system (such as that provided
by a muffler vs that provided by a straight pipe) generally improves low end
torque. If both of these generalizations are true then I would conclude that
switching to a straight pipe is likely to result in a loss of low end torque
that may well be more noticeable than any gain in turbo performance. Keep in
mind we're talking about a wastegate limited turbo engine running moderate
boost pressures with catalytic converters still in place.
If adding a straight pipe does reduce low end torque then I would expect
turbo spool up to take longer as well. Turbo performance is dependant upon
the energy available in the exhaust. If the engine makes more torque at a
particular rpm then it is making more power and there will be more energy
available in the exhaust to drive the turbo.
Date: Sun, 31 Aug 1997 22:03:28 -0700
From: "J.J. DEMICK" (jj@supernal.net)
Just wanted to let you know that I have been reading this site for about
a year now. I have torn down engines, replaced head gaskets for people
in 6 hour including milled head and the extra's. (live in Seattle). I
read alot about people wanting "performance exhaust's" Hears a story.
HKS exhaust...(Love HKS dont get me wrong) but PLEASE!!! Greddy, who
ever!!! PLEASE. (we are talking na/mk1) I got a 89 N/A well built (dont
want to get into details and sound like everyone else, unless you want
to know) What your readers are not understanding is sure put the twin
power on, the intake (flowmaster, K/N whoever) But if the cant " pass
gass" Or have a "flowing exhaust" your not doing anything. I believe
everyone should realize that you get the "ass end of the car flowing
first then start up front." Now here's the solution (you sitting down?)
You rip that dam piece of crap stock cat out! and you put in a high flow
cat (little bigger but Dam good) then you run 21/2 inch pipe out order a
2 1/2 inch U pipe to take the turn ( DO NOT BEND YOUR OWN!) then run a 3
chamber flowmaster, then from there put a few bends in the pipe and slap
on a 3 1/2 inch brospeed single tip. Now you have a FLOWING exhaust
system with a single tip, not too loud but enough to sound mean.
performance wise, it smokes HKS, and many other's. (I have had three
different exhausts before this one was thought of, all three were bult
on "performance exhausts".) everthing can be bought from any muffler
shop in town, hell buy the 3 chamber out of jegs magazine for
$50.00!!(shipped) the U bend is about $30.00 from Ca, the brospeed tip
can be bought for $35.00 from a local auto parts store, and the rest can
be done by any one with a welder. (oops the high flow cat will getcha
though. I got mine from Brice at Alamo Autosports in arlington, been
working with Brice for years, for $200.00 ((my price))
Well there it is. Had to tell someone. I work on many Mr2's in the
Seattle area and some have done it and love the NEW performance it
offers.
J.J.